The number of confirmed cases of swine influenza A H1N1 continues to grow. According to the World Health Organization, the list of countries where the virus has been detected now stands at 11 with Switzerland and the Netherlands reporting their first cases of the virus. And for now, the WHO is maintaining its pandemic threat warning at Phase 5, the second-highest alert status.
The World Health Organization reports a 75 percent jump in the number of confirmed swine flu cases worldwide since Wednesday. Mexico and the United States account for much of the increase.
The WHO's Phase 5 threat warning signals that a global pandemic could be imminent, but has yet to develop, with human-to-human transmission occurring in many geographical locations.
"There is nothing which epidemiologically suggests today that we should be moving towards Phase 6," said WHO Assistant Director-General, Keiji Fakuda.
A growing number of countries are either discouraging or banning travel to and from Mexico, where the first cases of swine flu were reported and where the virus is suspected in thousands of infections and more than 150 deaths.
The Obama administration says there are no plans to close the 3,000 kilometer U.S.-Mexico border. Rather, the U.S. government is urging common-sense steps to prevent virus transmission and distributing millions of doses of anti-viral treatments to health officials nationwide.
Meanwhile, expedited efforts are going forward on several continents to develop an effective vaccine for the new strain of influenza. European Union health ministers pledged to pursue an effective and safe vaccine without delay.
Angus Nicoll of the European Center for Disease Prevention says that at this point no one knows whether the virus will become more or less virulent in the months ahead. "It is quite possible with an influenza virus, a pandemic influenza virus that it gets worse over time. We just have to wait and see for that," he said.
A similar effort to develop a vaccine has been launched in the United States. But the interim director of the U.S. Centers for Disease Control and Prevention, Richard Besser, says it will be months before any decisions are made about mass-inoculations.
"The target would be to have this vaccine ready for the fall flu season, so that in addition to being vaccinated for the [common] flu, you would be able to be vaccinated for this [new] strain. But that decision as to whether we should vaccinate the public has not been made. And we will not know that until this [outbreak] goes much further, and we see whether this infection becomes more severe or goes away," he said.
Every year, tens of millions of Americans are vaccinated against influenza. But the current swine flu is a new strain to which humans have no immunity and against which existing vaccines offer no protection.